Positive-scavenging two-cycle internal-combustion engine.



v F. J. KIMBALL.

POSITIVE SCAVENGING TWO CYCLE INTERNAL COMBUSTION ENGINE.

APPLICATION FILEI JUNE 27, 19I4.

Patented Dec. 28, 1915.

3 SHEETS-SHEET l.

F. I. KIIVIBALL.

POSITIVE SCAVEN GING TWO CYCLE INTERNAL COMBUSTION ENGINE.

' APPLICATION FILED IUNEZI. I9I4.

1,165,515. Patented Dec. 28, I915.

. 3 SHEETS-SHELI 2- 4 I 1 yaww fggxr F. J. KIMBALL. POSITIVE SCAVENG INGTWO CYCLE INTERNAL COMBUSTION ENGINE.

APPLICATION FILED JUNE 27,1914.

3 SHEETS-SHEET3 Patented Dec. 2b, 1915.

s rains Parana @Fiditlfi.

FRANK J. KIMBALL, DE LOS ANGELES, CALIFORNIA.

POSITIVE-SGAVENGING TWO-CYCLE INTERNAL-COMBUSTION ENGINE.

T 0 all whom it mag concern:

Be it known that I, FRANK J. KnnsaLL, a citizen of the United States,residing at Los Angeles, in the county ofLos Angeles and State ofCalifornia, have invented a new and u'seful Positive-scavengingTwo-Cycle In- 'means for thereafter supplying a mixture of air and fuelto the cylinder for positive scavenging and charging action.

A further object of the invention is to provide, in an engine of thischaracter, means fol-postponing or breaking the compression byprolonging the period of exhaust, during a partof the compressionstroke, therebyenabling the expansion of the burnt .gases down tosubstantially atmospheric pressure, with resulting high economy, and

also enabling more efiective scavenging of the products of combustionduring this period of prolongation of the exhaust.

Another .object of the invention is to provide means for supplying waterto the partly compressed mixture of fuel and air, so as to keep thetemperature. of the fully compressed mixture from rising sufficiently toresult in premature ignition.

The accon'ipanying d *aw'ings illustrate an embodiment of my inventionand referring thereto: Figure 1 is a plan view of the engine, partlybroken away. Fig. 2 is a longitudmal .section, on line LL2'-U2 inFig. 1. Fig. 3 is a side elevation, partly broken away. F ig. i is a.section on line'.a': r* in Fig. 1. Fig. 5 is a section on line ww inFig. 1, with parts broken away.

It will be understood that my invention is applicable to an enginehaving any number of cylinders. In the drawings. it is illustrated asembodied in a single cylinder engine, having a crank case 1, a mainshaft 2, journaled on said crank case, and cylinder means mounted onsaid crank case and comprising a main cylinder 3, and a low pres-Specification of Letters Patent.

Patented Dec. 2%, 11915.-

Application filed June 27, 1914. Serial No. 847,572.

sure cylinder 4;, 'formed as an extension of the main cylinder. Atrunk-piston 5 working in said main cylinder, is connected by connectingrod 6 to crank 7 on shaft 2, and said piston is provided with anenlargement, or

flange 8, working in the cylinder i, said cylinder 4 being suiticientlylarger than. the cylinder 3 and the piston 5, to provide an annularcylinder chamber 9 between the said piston and the wall of cylinder 4.Piston 5 and the piston portion 8 are provided with the usual packingrings 10 and 10.

I prefer to use crank case compression for a preliminary scavenging ofthe main cylinder 3. and for this purpose the crank case is providedwith an inlet valve 11, normally held closed by a spring 12, and openedautomatically, by suction in the crank case, to admit air thereto. Thecylinder extension fl opens into the crank case, so that the piston 5 5operates to compress the air in the crank case on its outward stroke. Aconduit or pipe ll leads from the crank case to a scav enging inlet port16 in the wall of cylinder 3, and said cylinder is provided, oppositesaid inlet port, with an exhaust port 17, the piston having a deflector18, for deflecting the scavenging air so as to clear the cylinder moreeffectively.

The cylinder extension or low pressure cylg5 inder 4 is provided withinlet port 19 opening into inlet valve chamber 20, and with outlet port21, opening into a valve chamber 22. An inwardlyopening inlet valve 23is provided for valve port 19, and is normally held closed by a spring2i, and an outwardly openingvalve 25 is provided for outletport 21, andis normally closed by a spring 26.

Inlet chamber 20 communicates with fueb and air supply means, forexample a carbureter 31, of any suitable type. 'Outlet valve chamber22communicates, through a pipe .27, with a mixing chamber '29,'whichcommunicates, through a contracted duct, or

Venturi tube, 37, with a valve chamber 28 in the head 13 of the cylinder3. In order to provide suflicient space for storage or retention of acharge of air and fuel, compressed at low pressure by the cylinder 4,

until the main cylinder3 is ready to receive it, the valve chamber maybe provided with an extension or storage chamber 30. [in inlet valve 32for main cylinder 3 is provided in the mlve-chamber 28, and is normallyheld closed by a spring 33, so as to shut iii communication through theport 36, be-

tween said valve chamber and the cylinder 3, said spring being set atsuch tension as to allow the valve to open only when the pressure in thecylinder 3 falls to or below atmospheric pressure, during the opening ofthe exhaust port. The mixing chamber 29 is preferably circular, theinlet pipe 27 entering the same tangentially and the outlet pipe 37extending axially from said chamber, so as to produce a verticalwhirling motion of the mixture as it passes through said chamber. 1

Means are preferably provided for.sup-.

plying moisture to the mixture as it passes through the pipe 27, saidmeans comprising, for example, a water supply tube 38 connected with thepiping 41 for the water jacket 42 of the engine, and adapted to feedwater gradually to a receptacle 39 in a contracted portion 40 of saidpipe. Said water supply pipe may have a sight feed cup 43, check valve44 and manual valve 45.

Suitable means are provided for igniting the charge, for example a sparkplug 34 exposed in a chamber adjacent to the inlet port 36 in thecylinder head, said spark plug being connected to any usual means for Ithence through port'19 into the cylinder producing a spark thereat atthe proper moment.

In connection with the engine construction above described I may providemeans for breaking or postponing the compression, so as to reduce oreliminate the terminal pressure at which the exhaust gases aredischarged from the engine. For this purpose a supplementary exhaustport 48 may be provided in the cylinder, in position to be closed by thepiston say at about one half stroke, in its movement toward the head endof the cylinder. and an inwardly opening valve 49 is provided for saidport, said valve being normally held closed by a spring 50 and beingopened during the first portion of this inward stroke of the piston, bysuitable means. such as a lever 51, operated through rod by an eccentric53 on a shaft 54 which is driven from the main shaft 2 of the engine, bychain gearing or otherwise. This shaft 54 may also be used to drive thegovernor 57 which through lever and rod connections 58 controls athrottle 59 for the earbureter 31.

The operation is as follows: As the piston 5' moves outwardly. that is,away from the cylinder head 13. the piston 8 also moves outwardly anddraws a charge of air and fuel through inlet port 19. the valve 23opening automatically under the suction from the low pressure cylinderchamber 9, and the air being drawn through the carbureter 31 to thevalve chamber 20 and chamber 9. During this movement also, the pistoncompresses the air in the crank .ton 5, a supplementary chamber, so thatat the endof this outward stroke, the l crank case contains air underlow pressure, say about one pound per square inch, and the cylinderchamber 9. contains a charge of air and fuel. As the piston ber 30, thevalve 25 opening automatically under the pressure in the cylinderchamber 9. The storage chamber 30 is in this manner charged with amixture of air and fuel,

under low pressure, say about three to five pounds per square inch, thismixture being communicated through pipe 27 to valve chamber 28, and thepressure of the mixture tending to lift the inlet valve 32, which is,however, held closed during this compression -stroke by the pressure incylinder 3, and by the pressure of spring 33; so that the charge isretained in chamber 30 until near the end of thenext outward orexpansion stroke of piston 5. As the piston opens the ports 16 and 17 incompleting its expansion or outward stroke, any pressure.

which may exist in cylinder 3 is relieved by exhaustingof gases throughthe port 17, and

a preliminary scavenging is then effected by blowing of air from thecrank case through the ports 16 and 17 as above described. At the momentwhen the pressure in the cylinder is reduced by opening of port 17, the

. inlet valve 32 is opened by the pressure of the mixture thereon, therebeing at this time no back pressure on the inner fac e, of the valve,and a charge of mixture then flows into the cylinder 3, expelling thefoul gases remaining in the cylinder. through the ex- 'haust port 17. Asthe piston starts on its mstroke, the supplementary exhaust valve 49 isopened by its operating means above described, and this valve remainsopen until after the piston 5 passes the port 48, so that in the firstpart of the instroke of the pisexhaust passage is maintained throughport 48 and valve 49, permitting a positive scavenging actiondue to theinflowing of the compressed mixture at low pressure from the storagechamber30, through the inlet valve 32. this mixture of fuel and airdriving the remaining foul gases out throughthe port 49. until said portis closed by piston I) passing over it. I prefer to so adjust thetension of the controlling the burnt gases to substantially longed, soas this means 1 tion of the pipe 27, wherein taken up by the mixturemoving at high' high pressure in cylinder 3, which drives the pistonoutward in the succeeding expan sion stroke. During this stroke theinlet valve 32 is held closed by its spring 33 and by the pressure inthe cylinder 3, and the supplementary exhaust valve 49 is held closed bypressure of its spring 50 and by the pressure in said cylinder.

' By the opening of exhaust valve 49 during the first part of the inwardstroke of the piston. the period of the exhaust is pro to p"rmit of amore effective scavenging action, and the influx of fresh mixture fromthe head'end of the cylinder at this time further insures complete andpositive scavenging. Moreover, the postponement of compression tohalf-stroke, or thereabout, results in decreasing the ratio ofcompression to the expansion in the next out-stroke, so that the burntgases may be expanded substantially to atmospheric pressure, withresulting higher economy, as well as a comparatively noiseless exhaust.By obviate the great waste of energy which is ordinarily incurred in thedischarge of exhaust gases at high temperature and pressure, since theexpansion of atmospheric pressure also reduces the temperature thereof,the heat of the gases being utilized in doing work.

In order to keep the temperature of the gases on compression thereof,from rising sufficiently high enough to cause premature ignition, watermay be supplied to the partly compressed mixture as it passes throughthe supply pipe 27 and mixing chamber 29, by opening valve 45, allowingwa er to flow from the circulating water system of the en. gine, throughpipe 38 to the contracted porthe water is velocity. I

The pressure in the storage chamber 30 is determined by properlyproportioning the capacity of such chamber and its connections withrelation to the capacity of the low-pressure cylinder chamber 9. I havefound that by using a pressure of five pounds or so, per square inch, apositive scavenging effect is obtained. giving a fullcharge of cleanmixture.

By provision of the automatic spring con trolled valve 32, I am enabledto admit the fuel and air mixture at the head end of the cylinder, awayfrom the exhaust port, and

thereby obtain most efiective scavenging and charging actions,withoutthe use of special valve-operating cams or other mechanism for openingthe valves at the proper time, the time of opening of the valve beingcontrolled automatically by the pressure in the cylinder itself, as thevalve will remain closed until this pressure is eliminated by opening ofthe exhaust port, at the end of the expansion stroke.

What I claim is:

1. An internal combustion engine comprising a main cylinder and piston,a low pressure cylinder and piston, said pistons be- .ing connected tooperate simultaneously, means for admitting fuel and air to the lowpressure cylinder, storage means for receiv ing compressed mixture offuel and air from the low pressure cylinder, sa'id main cylinder beingprovided with an exhaust port opened by the piston at the end of theexpansion stroke, and with a supplementary exhaust port controlled bythe movement of the piston to maintain an open exhaust during the firstpart of the compression stroke only, and valve means for admittingcompressed mixture of fuel and air from sai storage means to the maincylinder after the opening of the first named exhaust port and duringthe opening of the supplementary exhaust port.

2. An internal combustion engine comprising a main cylinder and piston,a. low pressure cylinder and piston, said pistons being connected tooperate simultaneously, means for admitting fuel and air to the lowpressure cylinder, storage means for receiving compressed mixture offuel and air from the low pressure cylinder, and an inlet valve meansfor the main cylinder communicating with the mlxture storage means andopening under the pressure of the compressed mixture, to admit mixtureto the main cylinder when the pressure in said cylinder is re-' lieved,and said main cylinder being provided with an exhaust port opened by thepiston to relieve the pressure therein at the end of the expansionstroke and with a supplementary exhaust portcontrolled by the movementof the piston to maintain an open exhaust durin the first part of thecompression stroke, add to close such supplementary exhaust during theexpansion stroke.

3. An internal combustion engine comprising a main cylinder and a lowpressure cylinder, pistons working in said cylinders and connected forsimultaneous operation, valved inlet and outlet means for said lowpressure cylinder, fuel and air supply means connected to the inletmeans for the low pressure cylinder, a storage chamber connected to theoutlet means of the low pressure cylinder, and a valved inlet meansprovided with a mixing device and connected with said storage chamberaud with the main cylinder, to

&

admit mixture to said cylinder from said storage means.

4. An internal combustion engine cornprising a main cylinder, a lowpressure cylinder, pistons working in said'cylinders and connected forsimultaneous operatimnmeans for supplying fuel and air to the lowpressure cylinder, a storage chamber connected to receive compressedmixture from the low pressure cylinder. said main cylinder beingprovided with an exhaust port opened by movement of the piston, and withan inlet valve connected with said storage chamber to admit air and fuelfrom said chamber to the main cylinder when the pressure in saidcylinder falls on opening of said exhaust port, and said main cylinderbeing further provided with a supplementary exhaust port opened bymovement of the piston, during the outer portion of the piston stroke,an

engine-operated valve connected to said supplementary exhaust port, toshut off the exhaust through said port during the expansion stroke ofthe piston, and to open said exhaust during the first portion of theinward stroke of the piston.

5. An internal combustion engine comprising a main cylinder, a lowpressure cylinder, pistons working in said cylinders and connected forsimultaneous operation, means for supplying fuel and air to the lOWpressure cylinder, a storage chamber connected to receive compressed airand fuel mixture from saidlow pressure cylinder, a compression chamber,cooperating witlrthe engine piston 'means for compressing air during theexpansion stroke of the piston, said main cylinder being provided withan exhaustport and with a scavenging inlet port, opened by the piston atthe end oii its ex pansion stroke, said scavenging inlet port beingconnected to said compression chamher to supply air to the main cylinderfor scavenging, when said exhaust port is open, and said main cylinderbeing further provided with a spring-controlled inlet valve connectedwith said storage chamber to supply air and fuel mixture to saidcylinder when the pressure therein falls on opening of the said exhaustport, and said main cylinder being further provided with a supplementaryexhaust port opened by the piston during the outer portion ofits stroke,and an engine-operated valve connected to said supplementary exhaustport, to shut oil the exhaust through said port during the expansionstroke of the piston, and to open said exhaust during the first portionof the inward stroke of the piston, so as to provide for compressiononly during a portion of the i inward stroke.

6. In an internal combustion engine, the combination with a maincylinder'and a low pressure cylinder, and with pistons working in saidcylinders and connected for simultaneous operation, of means forsupplying air and fuel to said low pressure cylinder, a'

storage chamber connected to said cylinder to receive compressed mixtureof air and fuel therefrom, a circular mixing chamber, an inlet pipetherefor connected with said storage chamber and connected tangentiallyto said mixing chamber, and said mixing chamber having an axiallyextending contracted outlet, and a valve for controlling communicationbetween said outlet and the main cylinder.

In testimony whereof I have hereunto set my hand, at lios Angeles,California, this 22nd day of June, 1914.

FRANK J. KIMBALL. Witnesses: v I

C. E. ALLYN, A. P. KNIGHT.

